In my previous company we were evaluating ExtJS v/s SmartClient, we did lots of comparisons and SmartClient had lots of cool features and was up to the par with ExtJS but the only thing that was lacking here was traction in the community, finally we decided on ExtJS. When evaluating an open source product I give lots of importance to open source community around that product, namely I look for
- Does this product has a mailing list, how active is the mailing list? how many messages are posted by users per month and are there enough discussions going on?
- How frequent are releases for this product?
- How many users have written blogs and tutorials about this product?
- Are there any books from OReilly or Manning about this product (I rate Manning and Oreilly books better then other and I hate the SAMS 24 days books)
- How many bugs are closed,Open,In QA for this product
- How old is this product? Old product have their own baggage so if a newer kid is on the block with a vibrant community I would compare features and go for it.