I tried it for a while and couldn't quite get used to it. OK for coding, but hard to get to elsewhere - e.g. placing an ebay bid of !"£.$% lol! However, I'm not a numpad user... for those who are, the switch would be a lot easier to get used to I think. All the same, when I gave up, I did intend to try it again at some point.
Here's the Autohotkey script I was playing with (I called it PlingOne.ahk

)...
#NoEnv ; Recommended for performance and compatibility with future AutoHotkey releases.
SendMode Input ; Recommended for new scripts due to its superior speed and reliability.
#SingleInstance Force
#HotkeyInterval 999999
#MaxHotkeysPerInterval 9999
#UseHook On
;$+1::
;if GetKeyState("Capslock", "T")
; Send +1
;else
; Send 1
;return
+1::Send 1
1::Send +1
+2::Send 2
2::Send +2
+3::Send 3
; 3 -> '+'
3::Send +{SC00D}
; AltGr 3 -> '£'
;<^>!3::Send +3
<^>!3::Send {ASC 156}
+4::Send 4
4::Send +4
+5::Send 5
5::Send +5
+6::Send 6
6::Send +6
+7::Send 7
7::Send +7
+8::Send 8
8::Send +8
+9::Send 9
9::Send +9
+0::Send 0
0::Send +0
; '['
SC01A::Send +{SC01A}
+SC01A::Send {SC01A}
; ']'
SC01B::Send +{SC01B}
+SC01B::Send {SC01B}