Anyone who says they are slow through tight trails is either too unfit, unable to ride quickly or hasn't ever ridden a good 29er.
They are brilliant – I have 2 – geared and SS, and 2 26" bikes which don't really get used any more. The 29er cuts the chatter bumps right out, it rolls over things so much more smoothly, you don't really notice the extra few grams (my 29er race wheels are 300g heavier than my 26" ones and the tyres are 100g heavier each, so 500g overall – not a huge amount). I'm using the geared one for racing over the winter. 2 races, one win and a 2nd so far.
Riding the 29er back to back with the 26" bike at Dalby this year, on the NPS loop, the 29er was faster. Far more control on the big rocky sections like Worry Gill, plus all the dropoffs look and feel smaller as the wheels are larger. Riding a 26" bike now feels like riding a BMX – the wheels keep disappearing into holes and all the trails feel less smooth.
I am seriously considering a 29er race bike for next year – I have a choice of 26 or 29 – and at the moment I think it'll be a 29er. The only thing holding me back is a lack of decent mud tyres for Mayhem and SITS – Schwalbe need to do the mud shark 1.5 in a 29er… And lightweight suspension forks – no 29" SID yet. Even so, I'll probably go 29er.
GB