"1 million row Monte Carlo simulation in LO Calc 4.x, re-calculation time around 25 sec, same in MS Excel 2010, around 10 sec (core-duo/3Gb ram) so yes slower on bulk arithmetic I'll grant you."
If you're doing this kind of shit in a spreadsheet then you need to be tarred, feathered, set on fire and drummed out of town on a rail.
Just because you can run a regional health authority on MS Excel(*) Doesn't mean you should.
(*)Yes, really(***) - and when my business used the same programmers at insistence of one of the directors(**), we found 20% discrepencies in accounting answers vs using quickbooks after it was realised the Excel system was a hopeless piece of crap for a business less than 1% of the size of the RHA. (and it didn't produce output acceptable to any accountant, unlike QB)
(**) "Quickbooks is expensive. We can't afford it." etc etc etc
(***) I've been informed that the RHB in question is not the only one to do so.