I have 4 SQL Servers running on Quad Xeon processors with hyperthreading enabled. In the past I have had one system shutdown (found out it was bad install of SQL Server, formatted and started from scratch and has worked great ever since.)
Another system would shutdown and restart. Bug with UDF's and SP3 fixed the problem.
Otherwise I have had good experience. I don't know if Hyperthreading has helped or hindered my processes though.
Do make sure you have Service Pack 3 however.