MSN Hotmail users will enjoy a variety of new features today. First of all, a long delayed upgrade in mail box size is being rolled out across new sign ups, as well as existing members. After a 30 day "trust" period (size starts at 25Mb) new users get upgraded to the larger sized mailbox. Hotmail users will be restricted (like Gmail) with a 10Mb cap on message size. Hotmail have also added addition photo features, including the ability to touch up photos and compress them. Microsoft wants to make it easier for Hotmail users to share photos online.
Hotmail have also updated their anti-virus and anti-spam software. Hotmail, long viewed as a major target for spammers, is attempting to crack down on the junk mail that may be sending its users elsewhere. Microsoft has introduced the SenderID framework, an anti-spam system. How effective this will be is still unknown; SenderID has gained little support from the open source community (i.e. apache, spamassasin - major tools in email) and until Microsoft resolve this by relaxing the licensing issues the technology could see reduced uptake regardless of how effective it is.
One major improvement that non-US customers will enjoy is country specific hotmail domains. For example, users in the UK can now register at hotmail.co.uk, as can French users at hotmail.fr. This improvement will probably be the most noticed, as the squeeze for names on the US domain has become a growing problem for new users.