I tested Ashampoo Office 2008 and 2010, which are re-branded Soft Office 2008 and 2010 recently. I can tell by now, this is a fantastic product. In addition to directly writing and read MS Office format files (Word, Excel and PP, although 2008 version writes doc and xls, but 2010 version writes also docx and xlsx) they have an option to be officially installed on a flash drive as portable applications and used on any PC from those USB sticks. When installed as portable on usb, SoftOffice 2008 takes about 50 M and 2010 version portable takes about 100M on USB stick.
Comparison with Gnumeric, which I used to use before discovering SoftOffice both are excellent, hovever:
1. Neither one has pivot tables capability
2. Gnumeric does not handle MS Office 2007 files
In a word, SoftOffice (aka Ashampoo Office) is replacing MS Office on my PC. SoftOffice is way faster than MS Office 2007 and feels faster than MS Office 2003 and if you do not need pivot tables in spreadheet, I do not see any significant difference in functionality.
At this point SoftOffice 2008 can be obtained free and SoftOffice 2010 has a small retail price - about 10% of MS bloat.
Lightning fast SoftOffice is key for me.