When REBUILDing indexes on SQL Server, what bearing does tempdb & LOG disk speed have? Say I have the a data disk that is 50x faster than the LOG and tempdb (measured by Random Write speed) disk. (Don't ask why that's something we'll be fixing if needed)

I have a table that's got 19 million rows with about 30 indexes (so basically non trivial).

How much of a factor would the disk speed of the LOG &amp; tempdb than if I was to have the same disk speeds as the data disk.

Edit:
Some more stats.

We have moved the LOG to the RAID data drive as test and unfortunately there was not improvement in the speed of the the REBUILD. It still too 1 hour.


tempdb is on it's own Raid10 array 
LOG    is on it's own Raid10 array
Data   is on it's own Raid10 array
RAM > 100 Gb (yes 100Gb) and no limit on SQL using it for data or index creation


Note this is not a transactional system, rather a Data Warehouse.
Indexes are treated the same as any other data modification i.e. they are written to the log.  The performance of your log will directly impact the performance of all writes to your database.  If your LOG drive is 50 times slower that your data drive, you have serious performance limitations and should consider rectifying that as soon as possible.