Guys,
Just want to share my experiences when recently migrating from R65 to R75.
Note - We were assisted onsite with our firewall support partner.
(Smartcentre)
In our case we built a new Windows 2008 (32 bit) server as Checkpoint gateway does not work on 64 bit servers? We exported the database and a month of logs from our existing Smartcentre, but had to use specific tools as R75 uses a different database/log format than R65. The export process also identifies object names that are the same name but in lower case and upper case. R75 will only allow one name whether it is lower case or upper case. The reformatted database is then imported into the new Smartcentre server which has the same IP address/name as the old server. This maintains 'SIC' etc and you can see if everything is OK by using SmartViewMonitor.
(Firewalls)
Half of our firewalls were replaced with new hardware as the old firewalls did not support R75. The other firewalls were upgraded with IPSO 6.2 and R75. Note - IPSO 6.2 via Voyager now has a 'HA menu', which allows you to configure Proxy Arps and static routes etc on one of the firewall pairs and it is automatically updated on the other. Pretty neat

We swapped one firewall at a time so downtime was minimal and always re-introduced the new upgraded
firewall as the backup, then pushed the policy and then made it VRRP master so we could remove the other firewall and upgrade.
(SmartReporter)
We also installed SmartReporter which allows us to run reports on Security rules usage etc.
(Observations)
Our existing firewall CPUs are now lower utilisation and the R75 SmartDashboard GUI has been much improved.
SmartDefender has now been replaced by IPS. We already have a separate IPS solution, so we turned IPS off.
There are some other new 'Blades' that look very useful. 'User Identity' which allows you to use active directory to put a name to a users IP address and 'Application Awareness', which is the big thing at the moment and Checkpoint only recently came into the game.
(Issues)
We have an outstanding issue on duplicate log files on the SmartCentre which we hope to resolve soon after logging a fault ticket with Checkpoint?
We also have an outstanding issue installing the R75 GUI on an engineers laptop. Still investigating.
CheerZ