I have an SD7. Brilliant little thing, I bought it for the form factor. SD5 same but I don't like the Handycam format.
SD7 (and SD5) not very good in low light, but if you can do manual controls then there is a big improvement.
84minutes in HG (highest) 1920x1080x60i on an 8Gb card. 120 minutes at next down.
I think (and this is just me) that the Sony HDR-CX6/7 may be slightly better in low light on auto.
Other than that it is a great little cam and I am well pleased with it so far.
Off on holiday tomorrow for two weeks with 5 x 8Gb and 1 x 4GB cards. Hope I can find something to film.