There is a thread on this forum checking for start-up times:

There it is clear, big difference when using ssd compared to traditional HDD. Ever checked the actually read speeds of your drive?

Local ssd:

$ sudo hdparm -t /dev/sda

/dev/sda:

Timing buffered disk reads: 638 MB in 3.01 seconds = 212.29 MB/sec

HDD:

$ sudo hdparm -t /dev/sdc

/dev/sdc:

Timing buffered disk reads: 226 MB in 3.00 seconds = 75.30 MB/sec

My SSD ( 60 GB btrfs)

sudo hdparm -t /dev/sda

/dev/sda:

Timing buffered disk reads: 710 MB in 3.00 seconds = 236.28 MB/sec

My HDD (500 GB 7200 RPM ext4)

sudo hdparm -t /dev/sdb

/dev/sdb:

Timing buffered disk reads: 412 MB in 3.00 seconds = 137.12 MB/sec