You Bitcoin wallet doesn't take up too much space, it's the data about the block chain that is taking up all the bandwidth. Bitcoin relies on everyone keeping a copy of the block chain, to prevent any scams.
The standard client uses checkpoints, positions in the block chain, to know which blocks are considered safe and immutable by the developers, meaning they won't be checked as scrumptiously. The newest blocks are validated more thoroughly, to prevent malicious injection of data.
If you have a bandwidth limit, know that Bitcoin should only do this operation once - you're downloading the whole history of operations on Bitcoins after all. After that the downloads will be more managable.
The future Bitcoin clients could be operating as "lite clients", which will download far less data, but currently only alternative clients support that. It will also be possible that there will be clients developed that will use the Overlay Network, meaning they won't have to download basically anything at all, but again, the standard client does not support that.
If you want to operate on Bitcoins without downloading any data, you can try using some eWallets - they are basically websites that offer to host your Bitcoin needs. Some of them charge a small fee, and if they go down you will lose all of your coins, but on the other hand it provides a lot of flexibility and no need for downloads.
All in all, the standard client does require users to go through a bit of pain at the beginning, but after that it is mostly clear sailing. You can always try using an eWallet, but then you are entrusting the safety of your coins to someone else.
The "history of all transactions before it" is just a single number so that has no effect on performance. The issue is likely that newer blocks contain more new transactions. – David Schwartz – 2012-05-28T18:49:05.990
3The issue is that the most recent checkpoint is on block 168,000. For all blocks past there every signature is checked at block download time which takes a lot of CPU time and really slows the download. If you didn't reach block 168,000 (92%) yet, then you'll find it will slow even more when you do. – Chris Moore – 2012-05-28T20:04:46.737