There was a study presented on Google's datacenter SSDs as of late:
Conclusions are interesting:
SLC not more reliable than MLC
20-63% of SSDs develop a uncorrectable error in the first 4 years and 30-80% develop at least 1 bad block
Drives tend to have few or many bad blocks
Replacement rates for SSDs is lower, but their rate of errors is higher
Anyways, the full study is worth reading.
I suppose though that there is no real benefit in keeping SLC.