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well to be honest if stability is so important to you, then using any alpha/beta software is pretty daft!?
That said, I've found smartsection to be excellent stability-wise - there are a couple of little 'not finished yet' bits - but there's no issues at all that I've experienced with regards to errors, php screwups etc.
So if you're determined to run a site thats utterly dependent on stability using alpha modules - then I'd go with the latest?
Still think it's a pretty silly idea myself - instead give Marcan and co a nice Paypal deposit and I'm sure you'll be amazed at how quickly they can release a final version and at how stable they can make it when given support!