Regarding memory usage...
I have Monero running on a 64-bit Linux system with 2 GB of physical RAM. The daemon process is using about 1.25 GB. I have other applications running on the same system competing for RAM.
Syncing the node is slow and syncing the wallet is very slow, but other than that everything works fine. There is minimal swapping during normal operation (it hits the disk a bit when it processes blocks/transactions but nothing crazy). The log files don't show exceptionally high latency for processing blocks either. Overall system performance is fine.
Saving the blockchain (done every 12 hours by default I think) takes 17 minutes.
As I have guessed in the past, most of the blockchain data is untouched most of the time and can safely live in swap.
Typical output from vmstat 1:
r b swpd free buff cache si so bi bo in cs us sy id wa
1 0 3989448 15376 656 23932 0 0 0 28 75 150 0 0 100 0
0 0 3989448 15376 656 23940 0 0 0 0 73 141 0 0 100 0
0 0 3989448 15376 656 23940 0 0 0 16 73 139 0 0 100 0
0 0 3989440 15376 656 23924 88 0 88 0 132 237 4 0 89 4 <--processing a block
0 0 3989440 15376 656 23940 0 0 0 0 92 131 0 0 100 0
0 0 3989440 15376 656 23940 0 0 0 0 88 162 0 0 100 0
0 0 3989440 15344 656 23940 0 0 0 0 96 175 0 0 100 0
0 0 3989440 15344 656 23940 0 0 0 28 97 170 0 0 100 0 <- log file output being flushed to disk
0 0 3989440 15376 664 23936 0 0 0 12 91 160 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 87 162 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 78 141 0 0 98 0
0 0 3989440 15376 664 23940 0 0 0 0 80 163 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 65 118 0 1 99 0
0 0 3989440 15376 664 23940 0 0 0 0 75 140 0 0 100 0
0 0 3989440 15344 664 23940 0 0 0 0 63 120 1 0 99 0
0 0 3989440 15344 664 23940 0 0 0 0 90 174 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 72 129 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 70 131 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 83 153 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 78 157 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 77 144 0 0 96 0
0 0 3989440 15376 664 23940 0 0 0 0 91 167 0 0 100 0
0 0 3989440 15344 664 23940 0 0 0 0 93 184 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 77 147 0 0 100 0
0 0 3989440 15376 664 23940 0 0 0 0 85 160 0 0 100 0
ps:
monero 11789 3.0 73.9 4886856 1250456 pts/7 SNl+ 10:11 18:52 ./bitmonerod
