I haven't flown one personally but the Gentle Foamy and the Defiant are getting some pretty good press on the boards for beginner thermal performance. I would summarize what I have read as perhaps not as good as a GL or a Spirit, but pretty good.

Considering their rugged nature, they might not be a bad first sailplane.

Here are a couple of threads on the subject:
http://www.rcgroups.com/forums/showt...hreadid=211395
http://www.rcgroups.com/forums/showt...hreadid=185904