Other concerns for Verhaeghe: the service's beta status and the inability to buy more resources. He would also like Google to strengthen the licensing agreement with developers.

"Google has been very clear about its intention not to pry on code uploaded, but there is no track record," he said. "Specifically, you could raise the question of how uploading your code relates to 'publicizing' your invention, in the context of patents. Google should provide better legal protection there."

In Stockholm, Sweden, Colliberty Easy Publisher has been kicking App Engine's tires while wondering if Google plans to lift the limitation on the number of files -- 1,000 -- that developers can upload with an application, said Johan Carlsson, senior developer.

Mahmoud Arram of Cambridge, Massachusetts, is co-developing a commercial social-networking application with a partner, and wants to know whether Google plans to provide an automated way of migrating data out of App Engine and to support multi-threaded applications.

The level of clarity that Google's McDonald and Koomen provided for specific "wish list" features varied.

McDonald acknowledged that although App Engine provides a simple text search capability, Google is aware that it can be better. "We'd like to provide a complete full-text search in App Engine," McDonald said, declining to offer a timetable for delivery. "It's important to have."

He also stated that Google intends to make it easier for developers to migrate their data out of App Engine by supporting industry standards for those purposes. "The issue of data lock-in has been a little exaggerated," Koomen said. There are ways to migrate data out of App Engine today, but Google can simplify and automate the process, he added.

Likewise, Google is aware that developers would like to run multi-threaded applications on App Engine, but, in the meantime, Koomen points out that although apps are single-threaded, they are spun off into multiple servers running in parallel.

This allows applications to scale smoothly without developer interaction. "We can automatically scale and distribute the load among servers so it doesn't put stress into any particular instance or servers," Koomen said.

Google has no immediate plans to lift the limit of 1,000 files that can be uploaded with an application's code, McDonald said, adding that this doesn't apply to the number of files that an application's end-users can upload -- that's restricted by the amount of storage available for the application.

They were also very unequivocal in explaining that Google doesn't plan to support SQL databases as alternatives to Google's proprietary data store and GQL, which contribute to App Engine's "fluid" ability to scale.

Support for secure application communications is on Google's to-do list, although there is no public timeline for its delivery, McDonald said, adding that in the meantime, App Engine applications can use Google user accounts as an authentication mechanism.

Likewise, Google is also working on expanding support for more programming languages, they said.

Moreover, Google's licensing agreement with developers is very clear: An application's code, data and intellectual property belongs to its developer creators.

"We take that very seriously. Trust is one of the most important things we have going for us here at Google, and we want to make sure developers, through our terms and actions, understand that their code and data is theirs," McDonald said.

Stephen O'Grady, analyst at Redmonk, said Google is observing how developers use App Engine, to forecast the load their applications will place on its infrastructure and determine what volume it will be able to support. "This is about capacity planning," he said. "Google is keeping features at launch at a minimum to ensure adequate performance from everyone, until it can get a better profile of the demand."

Vishwanath Venugopalan, an analyst at The 451 Group, notes that while the number of App Engine accounts may be large, not many applications have been deployed yet, which gives Google an opportunity to continue figuring out best practices in this, a new market for the company.

However, Google needs to protect the positive and loud buzz around App Engine. "Undeniably there's a lot of developer enthusiasm, and we'd like to see how Google capitalizes on that," Venugopalan said. For starters, Google should prioritize supporting more programming languages and offering service-level guarantees to instill confidence in the service's performance and reliability, particularly after the outage it suffered in June.

Developers like Katz will be watching closely how Google tends to App Engine, and they seem at this point willing to give the company the benefit of the doubt regarding the recent outage and the current quotas on resources as things to be expected in these early days.

"I think the Google braintrust will solve issues that come up. It will be interesting to see how App Engine performs once quotas are removed," Katz said.

"For our little startup, I'm betting that by the end of the year App Engine will be stable and robust enough to handle the users for our niche commercial app even if we're lucky and it becomes popular," he added. "Outsourcing to Google is a calculated risk that takes into account my startup's constraints on cash and available programming time."