RX8PILOT  Numbers is cheap for a reason. It is a marginal piece of software that is certainly a fraction of it's inspiration XCEL. I generally love the simple Apple approach, but in this case it's not working. I have been trying a very basic layout that would take me 10 minutes in MS. For Numbers (I've been using it for a about 4 months), it's simply not working at all. For now, I'm sticking with MS for business. I don't have time in my day to learn a new way of doing on of the few things MS does very well---spreadsheets.   
(Version 1.0.3)

RICHARD TAYTOR  If you like jelly beans and Jobs, you probably like Numbers. I find the interface to be somewhat unfinished, though I'd probably use it if it weren't such a pig. The idle processor usage runs beyond 10% and it's ever-increasing/leaking memory allocation is already at a ridiculous 113MB RPVT (for a very simple table); more bloatware from Apple. Pathetic.

Alternatively, Tables is fast and uses system resources responsibly.  
(Version 1.0.3)

ANON BUD  Fabulous for my needs and with the full purchase of iWork '08, much cheaper than MS Office. Translates Excel spreadsheets just fine.  
(Version 1.0.2)

ORION MK. V  This update installed and runs no prob. Numbers really is a nice "lite" version of a spreadsheets. It's no number crunching powerhouse, but light number and easy integration with layout/graphic elements it's quite slick. Not surprisingly, it cut-n-pastes into the other iWork apps beautifully, and it's great to have a cell-based tool that can be used for charts/tables that it's so focused on massive number crunching, but more on usability.   
(Version 1.0.2)

THIRSTYROBOT  While not as refined as the other two apps that comprise the iWork suite, Numbers is adequate for basic spreadsheet needs. Given its performance problems when crunching large spreadsheets, I have my doubts about whether I can dump Excel quite yet. I would not have bought this app on its own, so I consider this one a freebie add-on to the very reasonably priced iWork suite.

I'm hoping that the new version brings the same kind of performance refinements that we've seen with Pages and Keynote to date.

I'd also like to see a better selection of expense-related templates. Can anyone recommend a good one that's currently out there?   
(Version 1.0.1)

NEURON  Although I greatly appreciate the design and usability (far better than Excel), Numbers is absolutely too slow when working with large datasets (>10,000 rows of data). Specifically, Find and Save are much, much slower than Excel 2004 (MacBook 2.16 GHz with 2 GB RAM, OSX 10.4.10). Its nice for making and formatting lots of small tables, but for analyzing large datasets... unusable.  
(Version 1.0.1)

ORION MK. V  Noticeable speed improvement on large tables, or when you have multiple tables that are text heavy. Some rendering problems with fonts occasionally now that weren't there before.  
(Version 1.0.1)